1. Technical Field
The present invention relates to a method for manufacturing a substrate, a liquid crystal display apparatus including an active matrix substrate and a method for manufacturing the same, and an electronic device having a liquid crystal display apparatus in its display portion.
2. Related Art
So far, a liquid crystal display apparatus including an active matrix substrate as an example of a substrate has been disclosed (see, for example, WO 97/13177, p. 23, p. 24, FIG. 17 and FIG. 19). A gate electrode as an electrode of a switching element portion (hereinafter, referred to as gate electrode portion), a drain electrode (hereinafter, referred to as drain electrode portion), and a source electrode portion, which are provided in this active matrix substrate, are formed by using a sputtering apparatus based on a dry deposition technique. Further, scanning lines as wirings provided in the active matrix substrate (hereinafter, referred to as gate wiring portion) or signal lines (hereinafter, referred to as source wiring portion) are also formed by using a sputtering apparatus based on a dry deposition technique. The gate electrode portion and the gate wiring portion are formed at the same time. Furthermore, the source electrode portion, the drain electrode portion, and the source wiring portion are formed at the same time.
However, with a recent tendency to enlarge the screen of a liquid crystal display apparatus, the substrate such as an active matrix substrate formed in the liquid crystal display apparatus has also been increasingly enlarged. With this enlargement, the lengths of the gate wiring portion and the source wiring portion formed in the active matrix substrate become larger than those of the conventional ones (before enlargement). As the lengths of the gate wiring portion and the source wiring portion become larger, the electric resistance values of the gate wiring portion and the source wiring portion become larger than those of the conventional ones. Since the electric resistance values of the gate wiring portion and the source wiring portion become larger, the power consumption of the liquid crystal display apparatus becomes larger. In view of this, the following idea has been considered: the thicknesses of the gate wiring portion and the source wiring portion are made to desired ones and the sectional areas of the gate wiring portion and the source wiring portion are made larger, thereby making the electric resistance values of the gate wiring portion and the source wiring portion smaller so as to achieve the reduction in power consumption of the liquid crystal display apparatus. However, in this case, as the thicknesses of the gate wiring portion and the source wiring portion are made to desired ones, the electrode thicknesses of the gate electrode portion, the drain electrode portion, and the source electrode portion of the switching element portion formed at the same time of the gate wiring portion and the source wiring portion are accordingly thickened. In the case in which those electrode thicknesses are thickened, the thickness of the switching element portion becomes larger than the desired thickness. When thus the thickness of the switching element portion becomes larger than the desired thickness, the shape of the section of the switching element portion becomes noticeably convex, so the local concentration of electric field is likely to occur within the switching element portion. Then, with the drop of the electric resistance value within a semiconductor portion, the generation of leak current as the performance deterioration of the switching element portion takes place. Accordingly, the wiring thicknesses of the gate wiring portion and the source wiring portion can be thickened only within the range, in which the performance deterioration of the switching element portion does not occur. Therefore, it is impossible to make the electric resistance values of the wiring portions sufficiently smaller, so there has been a problem in that the power consumption of the liquid crystal display apparatus is disadvantageously large.